


The Beginning

by Silcatian



Series: A Monstrious family [1]
Category: Undertale (Video Game)
Genre: Aftercare, Animalistic Reader, Animalistic Sans, Baby's first smut, Bara Reader, Bara Sans, Beast Reader, Beast Sans, Begging, Big Reader, Big Sans, Breeding, Claiming Marks, Dom/sub, Ecto-Tongue (Undertale), Ecto-Vagina (Undertale), Ecto-belly, Fluff, Gentle Sex, Hint of Master/pet play, Impregnation, Knotting, M/M, Mating Cycles/In Heat, Mentions of biting and scratching, Monster Heat, Mpreg, NSFW, Needy Sans, Nesting Instinct, No Ecto-Penis (Undertale), Oral Sex, Porn With Plot, Possessive Behavior, Possessive Reader, Pregnancy, Rough Sex, Self-Degration, Self-Shaming, Skeleton Heat, Smut, Soul stuff, Starting A Family, Sub Sans, Vaginal Fingering, degration, dom reader, ecto-stomach, pillow humping
Language: English
Status: Completed
Published: 2016-09-17
Updated: 2016-09-17
Packaged: 2018-08-15 14:04:47
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 1
Words: 2,099
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8059195
Author URL: https://archiveofourown.org/users/Silcatian/pseuds/Silcatian
Summary: Poor Sansy is in heat and needs his mate to come home to wreck him.





	

**Author's Note:**

> I've never written nsfw before, so please let me know if I need to add anymore tags.

He had been early, he was almost never early when it came to his heat cycle. Maybe it would start a day or two early or later, but this time it had been a week and it was far from his usual heats. That was if his throbbing needy cunt had to say anything about it. Great, his mate had actually made his magic submit to him, his mate had displayed enough dominance and care to outweigh his own. It was getting harder and harder think as his thoughts crept back to when he and his kitten last fucked. The skeleton moaned as he finger fucked himself harder, god his mate’s cock stuffed him so wonderfully last time. His fingers weren’t enough, he needed his mate to fuck him, to claim him, to breed him. His magic had already formed an ecto-stomach and womb for their child. He wanted _____’s child so badly, to feel their growing child punching and kicking, to see how much bigger his belly would grow. Just the thought of him made him pitifully whine in need, he desperately needed his mate to come home and fuck him senseless, to fuck him so hard he wouldn't be able to walk or properly speak for weeks. Sans whined as he started to rut against the pillow with his mate’s scent on it, he hoped to whatever was out there that his _____ could come home soon.

 

\---------------------------

 

When you came home that night you knew that something was wrong, you could feel unstable magic and a scent that was driving your loins crazy. With a low growl you carefully crept up the stairs following that alluring scent of your mate. You could hear his moans, his whines, his begging and pleading, your name being said like prayer, it only made you growl in a lower deeper tone. When you opened the door you were greeted with a sight that made you furious. Your skeletal lover had not fully changed into his 9'ft tall more animal like form yet and he was fucking himself with a knotting dildo. How dare he try any way to make him feel release without your cock in his cunt! You marched over to your lover and quickly grabbed the fake cock away from him, he whined and opened his sockets to see you, a now dopey smile on his face as he stared at you with half lidded eyes.

 

He was about to purr until he saw the rage on your face. “_____ wha-“ Sans was about to ask what was wrong until you forcefully slammed him down on the bed and straddled him. Your mate whined with pleading submission in his voice, “H O W D A R E Y O U! How dare you try to get off without me! I am your mate!” You growl raking your claws along his arms making him moan and lean into your harsh touch. “I guess I’ll just have to punish you, heh knowing you, you probably want that don’t you? You want me to fuck you so hard you won’t be able to walk for months, don’t you?” Sans moaned and shivered at the thought as he started to pant, he didn’t want his mate to keep talking anymore, he wanted to be fucked and bred this month god damn it.

 

“P-Please _____, I-I need you inside! I n-need you to b-b-breed me, please master!” No sooner than those words left Sans’ mouth did you ram you hardened cock into his ecto-pussy making your mate roar in pleasure to finally have his walls stretched so beautifully. “Fine, I’ll breed you my little slut. I’ll fill you up with my magic and claim your womb. Once this is over you’re going to regret your heated wishes.” You promised as you started to move, but you didn’t move fast. Oh no. In fact you were moving at a snails’ pace making your skeleton monster whine in frustration, but he didn’t dare try to force you to go faster in fear that you would stop all together. “Oh you didn’t think you’d be getting out of your punishment did you? Maybe a week at going this pace and not tying my knot with you should be enough.” You smirked as your mate’s expression looked heartbroken as he whined in need. No, no, no! He couldn’t stand this at all for a moment let alone a week and with no knot tied to him! He needed you to fill him up with your seed so he can having your baby bones! He’d do anything to get you to go faster and to be rougher with him. “P-Please master, I won’t do it again I promise! J-Just fuck me like the little bitch I am!” You only chuckled darkly and shook your head, he was not getting out of his punishment!

 

\------------------------

 

True to you word, you kept up the slow pace until your lover actually started to cry and sob from how much his cunt hurt from you being so gentle, the poor skeleton only got through five days of his punishment. You decided to have mercy on him and began to fuck him hard and fast that made him cry out in both pleasure and relief. However, to keep the punishment going you wouldn’t knot inside him for two more days. He didn’t really get a chance to complain as he was getting fucked out of his mind. You did your very best to continue fucking him whenever you could, even if he passed out on you more often than not from over stimulation. Sans sometimes was able to make the two of you stop to eat and drink and use the bathroom as it would be too dangerous to just have sex non-stop for either one of them.

 

Once your mate’s punishment and you finally tied your knot in him did you both cry out in sheer bliss. Sans moaned at feeling his womb getting filled with your cum, happy tears sprang at the corner of his sockets at the thought of your children inside him. He knew that they would look more like you in what type of monster your child/children would be, but maybe they’re bones would be sturdier or they would have his sockets or maybe some of his magic. The skeleton wrapped his arms around his belly, his sockets filled with hope as more of your magic kept spewing into his tight cunt to pool into his womb. He knew for sure that this batch of kiddos wasn’t going to be his only one. Oh no. You’d fill him up with more soon enough whether he or yourself were in heat or just want to fuck. Once your knot untied him you began ramming back into him again, you could tell by the look on his face that he needed more of your cum, that his womb and pussy wasn’t full enough with your rushing hot seed. Your poor little whore. His womb and stomach would grow soon enough with your children in this month of heat, you’d make sure of that.

 

\---------------------

 

After the month was over Sans opened his eye sockets groggily as his hands instinctively went to touch his belly. It had swelled. A purr rumbled deep in his ribcage as he could feel the tiny little souls slowly growing inside him, he had the biggest grin on his face when he saw your put your larger hands on top of his. He felt so wistfully happy, contented, and save in your embrace. Sans knew nothing bad would ever happen to him or your children so long as you were around, it was your job to guard your mate with your unborn babies now. Being a pregnant monster was very dangerous, most of the ‘mother’s’ magic was going to be used to help the child/children’s soul grow so they wouldn’t be able to attack or defend themselves against any kind of threat. Sans however was not only using his magic for the babies, but for his necessary parts as well which put him in more danger than others. That really wasn’t good for the skeleton at all, but you’d be damned if someone so much as thought about looking at your mate without permission.

 

You cooed sweetly at your mate as you peppered his face with gentle sweet kisses and messaged and kneaded his belly. Your skeleton lover completely relaxed as he sighed and closed his eye sockets enjoying your sweet words and gentle touches. This was only the beginning for both of you, you both would have to set up names, make nurseries, tell your friends and family the good news, maybe have a baby shower, and so much more. But right now you were both content to just bask in each other company and have a lazy stay in bed day all day long.

 

Your gently licked over the claiming mark on your lover’s neck vertebrae as he purred louder at your affection. “How many are in there? Or is it not that clear yet?”

 

“Um, I think maybe two or three. It’s a bit hard to tell right now, but I don’t think we’re only havin’ one kid.” Your mate said as he tried to feel how many souls were in his womb.

 

“Sounds about right for my species.” You chuckle. “Are you feeling okay? Was I too rough with you?” You could see the marks from your claws and teeth on his sturdy bones.

 

“I’m a bit sore and we could probably use a bath, but the bed is quite comfy right now.” Sans didn’t want to get up and face the day just yet. He wanted to take another nap and just be in his happy lazed state all day.

 

You huffed in amusement as you got out of bed causing your lover to groan in protest, you shushed him as you carefully picked him up and walked into the bathroom. You set him down on the toilet as you started to get the bath ready for the two of you, after this you’d make breakfast for the two of you if your stomach growling had anything to say about it.

 

Sans was pouty to be out of your safe hold, but he soon pacified himself by rubbing his growing ecto-stomach. He was going to be a parent with the monster he loved, god what would his brother say. The other monster’s weren’t nearly as nice as he was since coming to the surface besides the king and queen and that one yellow flower, whatever his name was.

 

The skeleton snapped out of his thoughts as he felt the tiny souls moving around inside of him, trying to get comfortable. His mate would have to help provide him with some magic to help him keep his ecto-parts for their babies as he would get tired eventually from keeping it up for so long. Sans made a mental note to look up some breeding information about your species of monster, he’d need to keep track of how long the little tykes would be in stomach until they were born.

 

You growled in frustration as the water wouldn’t turn on, of course the water would be turned off do to repairs. So instead you grabbed a washcloth and a room temperature jug of water and began to clean your mate by hand. Sans would whimper slightly when you would clean an overly sensitive spot, but he did his best to keep still like a good boy. You cleaned him until his bones were almost a blinding white and made sure to clean his tummy just in case. After that you put the jug away and left the dirty washcloth in the bathroom’s dirty hamper.

 

You picked up your mate again to have him sit down with a nest of pillows and blankets surrounding him, your mate deserved the utmost comfort after all. “I’ll be right back with breakfast, love. Anything specific you want?” You kissed the side of his skull while he blushed a bit.

 

“Some pancakes p-please.” He blushed a bit more when his stomach rumbled loudly bringing a chuckle out of you. His skull turned even redder when you kissed his tummy fondly.

 

“Coming right up, you just sit here relax and maybe watch some tv, okay.” You kissed the top of his skull before you went into the kitchen to provide your mate with fluffy pancakes. You snickered to yourself when you could hear light snoring coming from the family room.

**Author's Note:**

> Beastfell was created by: http://www.get-rammed.tumblr.com
> 
> Please support the creator!


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